Method and system for reducing oversized holes on turbine components

Abstract

A system is disclosed for reducing an internal diameter of a hole in a metal substrate. The system includes an electrospark device having an electrospark torch and an electrode holder rotatable about an axis. An electrode is removably supported in the electrode holder. The electrospark device configured to apply a coating of a material of which the electrode is formed, to the substrate on an inner wall of the hole when the electrode is rotated within the hole.

The invention claimed is: 
     
       1. A method of reducing an internal diameter of a hole in a metal substrate comprising:
 providing the metal substrate having a hole penetrating the metal substrate; 
 providing an electrospark deposition (ESD) device, the ESD device configured to receive a rotary electrode supported axially in the ESD device; 
 centering the electrospark torch over the hole in the substrate; 
 inserting the rotary electrode into the hole to a predetermined length below a top surface of the metal substrate; 
 maintaining constant the predetermined length of insertion of the rotary electrode in the hole; 
 applying the electrode to the substrate on an inner surface of the hole; 
 rotating the rotary electrode in contact with an inner wall of the hole; 
 applying an electrospark process; and 
 depositing an alloyed coating on at least a portion of the inner wall along the inner wall to reduce the diameter of the hole by a thickness of the coating. 
 
     
     
       2. The method of  claim 1 , further comprising repeating the previous step of depositing an alloyed coating until a desired coating thickness is obtained. 
     
     
       3. The method of  claim 1 , further comprising finishing the top surface of the substrate adjacent the hole to provide a substantially smooth surface comparable to the top surface prior to applying the ESD device. 
     
     
       4. The method of  claim 1 , wherein the coating thickness is about 0.023″ inches. 
     
     
       5. The method of  claim 1 , wherein the diameter of the hole is reduced by about 0.046″. 
     
     
       6. The method of  claim 1 , further comprising forming a metallurgical bond between the substrate and the alloyed coating on an inner surface of the hole. 
     
     
       7. The method of  claim 6 , wherein the rotary electrode comprises an electrode material suitable for forming a metallurgical bond with the substrate. 
     
     
       8. The method of  claim 1 , wherein the step of maintaining the predetermined length of insertion of the rotary electrode in the hole comprises inserting the rotary electrode through a ceramic tube spacer. 
     
     
       9. The method of  claim 8 , further comprising positioning the ceramic tube spacer substantially coaxially with the hole in contact with the top surface of the substrate. 
     
     
       10. A system for reducing an internal diameter of a hole in a metal substrate comprising:
 an electrospark device comprising an electrospark torch and an electrode holder rotatable about an axis, wherein the electrospark device is positioned over the substrate and the electrode centered at least partially inside the hole, the electrospark device inducing a spark to metallurgically bond a coating on an inner wall of the hole to reduce the size of the hole; 
 an electrode removably supported in the electrode holder, wherein the electrode includes a consumable rotary electrode, the rotary electrode supported coaxially with the electrospark torch within electrode holder and the hole; and 
 a spacer positioned on a top surface of the substrate concentric and substantially coaxial with the hole, the spacer comprising a hollow bore for receiving the electrode; 
 the electrospark device configured to apply a coating of a material comprising the electrode to the substrate on an inner wall of the hole when the electrode is rotated within the hole. 
 
     
     
       11. The system of  claim 10 , wherein the spacer comprises a ceramic tube spacer. 
     
     
       12. The system of  claim 10 , wherein the electrospark device is rotatably supported within a robotic frame. 
     
     
       13. The system of  claim 10 , wherein the electrode is insertable into the hole through the spacer. 
     
     
       14. The system of  claim 13 , wherein the electrode is arranged to penetrate into the hole below the top surface of the substrate at least a portion of a thickness of the substrate. 
     
     
       15. The system of  claim 10 , wherein the electrode penetrates the hole by a predetermined length below substrate top surface. 
     
     
       16. The system of  claim 15 , wherein the substrate is a metal selected from the group comprising: carbon steels, low alloy steels, martensitic, ferritic, austenitic and precipitation hardened stainless steels, solid solution nickel/cobalt base alloys, precipitation hardened superalloys, wear resistant alloys, stellites; and titanium alloys. 
     
     
       17. The system of  claim 15 , wherein the spacer is disposed between the electrode holder and the top surface maintain the predetermined length of the electrode in the hole.